Ok, brand new here and looking for some help before I go out and blow money on new parts I dont need. Here is my situation.

1998 Ram 1500 5.2L 2WD starting acting up about 2 weeks ago. Shortly after starting and before the engine warms up to normal op temps the truck will randomly lose power and backfire while going down the road. In more detail, I can start the truck and drive for about 2-3 min before anything starts happening but after a few min the truck will lose power and start backfiring, I can clear it up by hammering the gas pedal all the way to the floor once or twice while driving and then the truck runs fine. It doesn't happen if I start the truck and let it warm up for about 5 min, but if I start and go it happens every time.

The truck is also idling rough when I first start it and before it reaches standard op temp, but again once it gets warmed up it seems to do alright.

Most of what I have read so far seems to indicate it maybe a bad O2 sensor, plugged the OBD ii into it today and the codes I got were P0455- Emissions System Leak and p0305 - #5 cylinder misfire, which could be because of a faulty O2 sensor.

I am going to go ahead and change the plugs/wires/cap just because, but what I am am looking for is confirmation that it is the O2 sensor that is causing the car to backfire and lose power before the truck warms up, before I spend the money to replace them. Thanks

 

Pre-cat oxygen sensor FTW.

#5 misfire might be caused by a failed PCV valve (or a blown plenum gasket). How's the oil consumption?

 

P0455 would be a large leak. Check/replace gas cap and all hose's for holes/crack's.

EDIT.Freeze from data from the scanner would help?

 

Oil consumption is normal, going to replace the gas cap for the P0455 code and will check hoses tomorrow, ran out of time today after fixing the ABS sensor which has been out for months, will probably do the Pre-Cat O2 sensor as well, since it seems to only be an issue before the sensor goes into closed loop after reaching normal op temps and with excessive accelaration, which was talked about in some other forums.

If its the Plenum Gasket which I will check, I heard Dodge will fix that for free due to a recall, anyone know anything about that?

 

Nope. Not gonna happen that way. No recall on the failed plenum gasket.

 

Yeah, I kinda figured that was the case, guess I will just change it myself. So back to my original question....The pre-cat 02 sensor is most likely the root of the problem?

 

The "root" of the problem is most likely the blown intake gasket.

 

I'm puzzled. By the time you hit normal operating temperature the PCM should already be in closed loop mode... and your initial post indicated that the symptoms were evident after a few minutes of operation but before reaching normal operating temperature, which would be after the PCM goes closed loop. ???

Changing the story makes it hard to give a reasonable answer to your question.

Since you're not having any oil control problems, I'd do the plenum test (because it's easy and free) and only concern myself with it right away if the test indicates a gross failure.

 

Uh, ok, maybe I am confused, but the PCM does not go into closed loop mode until the engine reaches normal op temp or when throttle is wide open. The problem only occurs if the vehicle is driven before the engine warms up. I didn't change my story, and since it is not occurring until several mins into driving I guess it could be possible the problem is within the PCM switching from open loop to closed loop mode, I don't know.

To make it simple, once the vehicle warms up there are no issues, I drove it 1200 miles from Iowa to Georgia last week, the only time I had a problem was right after starting the truck, driving down the road a mile or two, it sputtered and had no power for about 20 seconds, and then I drove the remaining 1198 miles without a problem. It does it every day I go to work unless I let it warm up for about 5-10 mins. If the truck warms up prior to driving, no sputtering or back firing, if I start it get in and drive away cold then after about 3-5 mins it will lose power and sputter? Sorry to be blunt and possibly slightly rude, just trying to get opinions of someone who may have more insight into what is causing this.

 

Not quite. The PCM will go into close loop just as soon as the 02 sensors warm up. Since they are heated, it doesn't take long. There might be an engine temp constraint as well, but, it is going to be rather low. (100 degrees, give or take.) at WOT, the engine goes into OPEN loop.

If you are having issues only when the engine is cold, I would look at the coolant temp sensor, or IAT sensor. Check fuel pressure as well.